Date of Award

1-1-2004

Degree Type

Thesis

Degree Name

Master of Science

School

School of Natural Sciences

Faculty

Faculty of Communications, Health and Science

First Advisor

Associate Professor Pierre Horwitz

Abstract

In a salinised landscape farm dams may represent the last truly freshwater surface resource, and therefore provide refuge habitats for the biota of wetlands affected by increasing salinity. One wetland threatened by increased salinity in south-west Western Australia is Lake Toolibin. It is listed as a Wetland of International Importance under the Ramsar Convention in recognition of its high conservation value, and remediation actions to halt (and possibly reverse) further increases in salinity are being undertaken at this wetland. Farm dams act as aquatic refugia if they convey resistance and/or resilience to the biotic communities of a disturbed habitat. This study proposed to investigate farm dams as potential refuge habitats from which aquatic macroinvertebrate species could recolonise Lake Toolibin. To do this the physico-chemistry and aquatic macroinvertebrate community of fourteen farm dams surrounding Lake Toolibin, and Lake Walbyring an adjacent wetland that has remained comparatively fresh, were sampled in autumn and spring 1998. Comparison was made to previous studies of Lake Toolibin and Lake Walbyring to detennine if aquatic macroinvcrtebrate species from these wetlands were found in the broader landscape. Results indicate that the aquatic macroinvertebrate communities of Lake Toolibin and Lake Walbyring have been altered by increasing salinity. Both the physico-chemical and aquatic macroinvertebrate data collected from farm dams indicate a high degree of heterogeneity between sites, which is considered to be typical of that throughout the wheatbelt region of Western Australia. Of the 80 aquatic macroinvertebrate taxa previously recorded at Lake Toolibin, 41 were recorded in the surrounding farm dams and 30 from Lake Walbyring, in spring 1998. Of the 38 taxa recorded at Lake Walbyring in spring, 16 were either not collected or were rare in surrounding farm dams at the corresponding time. The aquatic macroinvertebrate community composition of farm dams was dominated by species of Coleoptera, Hemiptera, Chironomidae and Ostracoda. All species recorded from farm dams and Lake Walbyring in 1998 were considered to be freshwater species tolerant of a wide range of salinities, and widely distributed throughout south-west Western Australia. It was concluded that, when considered as a mosaic of habitat types and not as isolated systems, farm dams are important refuge habitats for the aquatic macroinvertebrate species of Lake Toolibin. The farm dams will provide a mechanism for the maintenance of aquatic invertebrate species richness and abundance. Refuge farm dam habitats can therefore contribute to the conservation and management of wetland biodiversity in a salinized landscape such as the Western Australian wheatbelt.

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